This invention relates to an improvement in a stator of a dynamoelectric machine capable of effectively preventing overheating of an iron core of the stator by cooling it with a cooling gas.
In these days, in accordance with an increase in the capacity of a steam turbine driven generator (called hereinafter a turbo-generator), iron loss of teeth portions and slot bottom portions of the iron core of the stator caused by leakage magnetic flux increases, which results in the rise of the temperature of the iron core to an extent of an allowable limit.
In a stator of a turbo-generator of a prior art shown in FIGS. 1 and 2, reference numeral 1 designates an iron core of a stator formed by laminating thin sector shaped iron sheets, hereinafter called the stator core 1. Armature coils 2 are fitted in slots of the stator core 1 which is clamped between end plates 3. Between the stator core 1 and the end plates 3 are disposed outer spacer blocks 4 which include long spacer blocks 4a located between the outer periphery 1c of the stator and teeth portions 1a of the stator core and short spacer blocks 4b located between the periphery 1c and slot bottoms 1b of the stator core 1. Ventilation buffer boards 5 are attached to the outer ends of the respective long spacer blocks 4a.
When the turbo-generator rotates, a portion of magnetic flux produced by a current passing through a field coil, not shown, vertically enters into the end portion of the stator core thereby generating an eddy current by which heat is generated in the stator. The density of the heat thus generated is particularly high at the teeth portions 1a and the slot bottoms 1b.
In order to remove this heat and cool the stator core, a cooling gas is used which flows from the rotor through tips of the teeth portions towards the slot bottoms 1b through the space between the spacer blocks 4a and the armature coil 2 along the end surface of the iron core and then towards the outer periphery 1c through the space defined by the side walls of the outer spacer blocks 4a and 4b, as shown in FIG. 2. Finally, the cooling gas reaches a chamber behind the stator core through the spaces between the buffer plates 5 and the outer spacer blocks 4b.
With the stator shown in FIGS. 1 and 2, since the cooling gas flows at a relatively high speed near the teeth portions 1a, these teeth portions 1a are effectively cooled by the effect of the rotation of a rotor, not shown, but the cooling gas flows at a relatively low speed near the bottom portions 1b, particularly, the end surface wall of the iron core which is deemed to be a main heat radiation surface, so that desirable cooling effect cannot be provided for these portions.